The Jet Leg App That Frequent Fliers (and NASA Astronauts) Swear By

Timeshifter was featured on Condé Nast Traveler's Bright Ideas in Travel 2026. Read the full list of winners here.What traveler, in their tedious shuffle back to the cramped rear of the plane, hasn’t gazed longingly at the lie-flat seats in business and first class? Surely the jet lag wouldn’t hit so hard if you could recline all the way back and get some proper rest, right? But that assumes jet lag is a sleep deprivation problem when, in fact, it’s not.“Everything that’s shared today publicly about how to address jet lag is wrong,” says Mickey Beyer-Clausen, co-founder and CEO of Timeshifter, a circadian tech company that aims to help travelers and shift workers adjust to new time zones and manage irregular schedules. “The biggest challenge is that circadian science is not publicly very well known.”Timeshifter is working to change that.Understanding circadian science begins with the fact that our each of our brains contain a tiny “clock,” a cluster of neurons called the suprachiasmatic nucleus, which is smaller than a grain of rice. This clock determines your body’s daily cycle of sleep and alertness—the circadian rhythm. “What we’re talking about is internal time,” explains Martha Merrow, a chronobiologist and visiting professor of circadian medicine at the University of Oxford. Everybody’s got their own internal time, which is unique to them, she says. Two people who share the same schedule can still have different internal times due to a range of factors, among them a person’s “chronotype,” which describes if you’re an early or late riser.Whenever you fly through a few time zones, your internal time can disagree with the actual time in your destination. That disagreement is jet lag. Yet much of the conventional advice about jet lag doesn’t address the key mechanism that helps your internal clock adjust. In short: It’s all about light, with sleep only playing a supporting role.“Sleep comes into it in two ways,” Merrow says. “One, if you don’t get enough of it, you really feel horrible. But the other way is that when you sleep, you actually are actively modifying your light environment by closing your eyes. So by sleeping at the ‘right time’ or ‘wrong time,’ you can help the phase shifting that you’re trying to achieve—or you can hinder it.” That exposure to light is “the main thing,” she says, that helps our internal rhythms adjust to wherever we are.That’s why snoozing on a flight doesn’t always help; it might shift your circadian rhythm in the ‘wrong’ direction. “You can sleep for eight hours and feel massively jet-lagged because all your circadian clocks are out of whack,” according to Beyer-Clausen. The solution is getting the timing right for light exposure, darkness, and sleep. “You have to personalize that for each traveler,” he says.That’s why the Timeshifter jet lag app asks for your age, your usual sleep times, your caffeine and melatonin habits, and your chronotype—early bird, night owl, or neither. Then you enter your flight numbers; the app pulls info about your departure and arrival times. With all that info, the app’s algorithm formulates a plan that begins days before you depart. It tells you when to expose yourself to light or avoid it; when to use and avoid caffeine; and when to snooze (and take melatonin, if you like).The protocols behind the app were first developed to support professional travelers who have no margin for error: NASA astronauts. Steven Lockley, Timeshifter’s co-founder and chief scientist, previously worked with NASA when he was associate professor at Harvard Medical School. “I had been a user of the science through Dr. Lockley in preparing for missions,” says Michael López-Alegría, a former NASA astronaut and investor in the app’s 2026 funding round. “Our bodies can naturally shift our circadian clocks about an hour a day, but using recommendations driven by science and provided through the Timeshifter app can accelerate that dramatically.” According to Lockley, following the guidance can help you shift as much as three to four hours a day.What does that look like in practice? I downloaded the app, entered my details for a theoretical trip (flying from my home in London to Tokyo and back), and checked what my Timeshifter plan looked like. Outbound, it told me to go to bed at 1 and 2 a.m. on the days before my flight. That’s easy enough for me, a hyperactive night owl. Harder would be the recommendation I avoid caffeine the morning I go to the airport (ouch, the brain fog), then sleep as soon as I board the plane (not going to happen with my nerves).I showed several personalized plans I generated to Merrow, who has no commercial relationship with Timeshifter. She confirmed the app generally aligned with the principles of circadian science. She also observed, as other reviewers of the app have, “it will be difficult to get excellent compliance” due to human behavior. “For instance, they expect [you to] sleep on much of one flight, but we know that drinks and a meal will be served in addition to the entertainment.”My success would depend on me following along to the plan, which might not always be possible. The Timeshifter app itself acknowledges such limitations. Its guidance explains that even if you can’t exactly sleep when it advises you to get some z’s, you could wear dark glasses to avoid light and still help nudge your internal clock.When you can follow the advice, it’s a game changer, according to Sem Verbeek, professional tennis player and 2025 Mixed Doubles Wimbledon Champion. Timeshifter’s user base includes a cohort of professionals like him—athletes, Formula 1 teams, astronauts—who need to be sharp when they land in a new time zone. “The biggest proof of concept for me came during my trip to Australia at the start of last season,” says Verbeek, who explained he would normally need to travel during Christmas to be prepared for the first week of the season. Timeshifter helped him “spend more precious time with my family and adjust more quickly and effectively than before.”Timeshifter gives you your first plan for free, then it’s $9.99 per trip or $24.99 per year, appealing to frequent long-haul fliers who can control their schedule. And due to partnerships with major travel brands, more of us ordinary travelers are getting free access. United Airlines’ Premier 1K members receive complimentary plans for each flight. In August, InterContinental Hotels expanded its partnership with Timeshifter; travelers staying at the brand’s properties get access with every booking. “The response has been great,” notes Tom Rowntree, vice president of global luxury and lifestyle brands at IHG Hotels & Resorts. “We’re able to support our guests to overcome some of the effects of long-haul travel even before they arrive.”But even pros can’t always follow the guidance perfectly. Verbeek admits his tennis matches can get in the way. “The most difficult part about following a plan is having to work around court times. We don’t always control when we can practice, let alone play our match,” he shares. “But a Timeshifter plan isn’t so strict that you need to follow it 100%.” Which is good news for anyone who, say, demands some espresso before navigating their way to the airport.